1. Field of the Invention
The present invention relates to the measurement of helicopter airspeed. More particularly, this invention pertains to a method for determining the horizontal airspeed of helicopters traveling above 20 m/s.
2. Description of the Prior Art
Commonly owned and allowed United States patent application Ser. No. 872,044 of Hassenpflug, et al., filed June 6, 1986 for "Method For Determining the Horizontal Airspeed of Helicopters in Low Speed Ranges", now U.S. Pat. No. 4,702,106 proposes a method that relies upon analytical computation for determining helicopter airspeed at velocities below 20 m/s. The content of this application is hereby incorporated by reference.
Unlike previous measuring methods, particularly those that employ pitot-static tubes and a probe that is rotatable about two axes, the proposed method referenced above requires no external sensor. Such a sensor is readily subject to damage, or may fail completely, due to external effects. Further, pitot-static tubes require relatively high power (heating) and, together with the requisite measurement converters, present a significant weight factor. The sole requirement of the proposed method is the provision of measurement signal generators for the required control units.
The objective of the invention is to provide an analytical method of determining the horizontal airspeed of helicopters in higher velocity ranges, i.e. in ranges v.sub.e &gt;20 m/s.